Congestion control in a telecommunications network

ABSTRACT

Congestion control in a telecommunications network, in which a method of congestion control in a transport network is provided. A buffer state of a buffer is monitored by dynamically sampling the buffer such that the sampling rate is adjusted in dependence of the buffer state. Also, a condition indicative of congestion is determined in response to a change of the buffer state exceeding a predetermined limit. In response to determining the condition indicative of congestion, a congestion notification message is created. The created congestion notification message may then be transmitted to a second network node. The second network node may subsequently compensate for a detected congestion on the basis of a received congestion notification message.

TECHNICAL FIELD

The present disclosure generally relates to telecommunications and, moreparticularly, to control of congestion in a telecommunications network.More specifically, the present disclosure relates to systems, methods,nodes, and computer program for congestion control in a transportnetwork.

BACKGROUND

It is a well-known fact that telecommunication networks utilizingresources shared between the users may experience congestion. Congestionmay, for example, occur when the sum of traffic of an ingress node ofthe shared resource exceeds the sum of the traffic of an egress node ofthe same shared resource. A typical example is a router with a specificnumber of connections. Even if the router has processing power enough tore-route the traffic according to an estimated link throughput, acurrent link throughput might in fact restrict the amount of trafficthat the outgoing links from the router can cope with. Hence, as aresult, the buffer(s) of the router may build up and eventuallyoverflow. The network then experiences congestion and the router mayalso be forced to drop data packets.

The normal behavior for any routing node is to provide one or morebuffers that can manage a certain amount of variation in input and/oroutput link capacity and hence absorb minor congestion occurrences.However, when the congestion is severe, the routing node will eventuallybegin to drop data packets.

Transmission Control Protocol (TCP) is a connection-oriented,congestion-controlled and reliable transport protocol. For TCP traffic,a dropped data packet will typically be detected by the sender since noacknowledgment (ACK) is received for that particular data packet and are-transmission of the data packet will occur. Further, the TCP protocolhas a built in rate adaptive mechanism which will lower the transmissionbit-rate when data packet losses occur and re-transmissions occur on theInternet Protocol (IP) layer. Hence, TCP is generally speaking wellsuited to respond to network congestion.

SUMMARY

The present disclosure recognizes the fact that current studies of thefifth generation of telecommunication networks (also known as 5G)describe a midhaul as part of the Radio Access Network (RAN)architecture. As will be appreciated, embodiments described throughoutthis disclosure relate to, but are not necessarily limited to,congestion control in this midhaul. The mix of different link speeds inthe network may introduce rate mismatch. Furthermore, congestion may becaused by the aggregation of traffic from many sources. Additionally, oralternatively, congestion may be caused due to differences in speedbetween the various network links. For example, congestion may occurwhen the demand for network resources exceeds the available resources atsome point of time in the network. As will be appreciated, too muchtraffic may create buffer overflow and data packet loss in the variousnetwork nodes and in the midhaul.

The present disclosure recognizes that existing solutions have tried tocope with similar problems in earlier generations of telecommunicationnetworks (e.g., 2G, 3G and 4G). However, this disclosure additionallyrecognizes that the existing solutions may in fact be inadequate for thenext generations of telecommunication networks, such as 5G or beyond.For example, in the protocol layers, congestion control (also sometimesreferred to as flow control herein) could be solved at respectiveprotocol layers, such as TCP (i.e., at Layer 4). Local Area Networkswitches could operate at link layer and provide pause signalingmechanisms to complement end-to-end flow control. However, for the newproposed 5G architecture, none of these functions would work in anoptimal manner and would typically not work at the Internet Protocol(IP) Layer (i.e., Layer 3). Hence, new congestion control mechanisms aredesired.

In order to give context to the embodiments described throughout thisdisclosure, reference is now made to FIG. 1 which schematically shows anexample of a midhaul architecture for a 5G RAN architecture. As can beeseen from FIG. 1, the midhaul architecture may comprise severaldifferent network nodes, such as Base Band Units (BBU), Routers, andPacket Processing Units (PPU). In the 5G RAN architecture, BBUs and PPUsmay be operatively connected over the midhaul using high speed links.The transport efficiency should advantageously be high and latency istypically required to be low. As a consequence, efficient flow controland overload protection is generally important in the transport part(a.k.a. the midhaul part) of the network, i.e. in the transport network,in order to keep the transport latency and buffer usage at low, oracceptable, levels. In the distributed 5G RAN architecture, thecongestion domain is typically between BBUs and PPUs.

As can be seen in FIG. 1, the 5G RAN architecture may also comprise aRadio Control Unit (RCU). The RCU may have a S1-AP interface. S1-AP isan abbreviation for S1 Application Protocol. S1-AP provides thesignaling service between E-UTRAN and the evolved packet core (EPC). Ascan also be seen in FIG. 1, the PPU may have a S1-u interface. S1-AP andS1-u per se are known among practitioners in the art and will thereforenot be further detailed herein.

In the 5G RAN architecture, the midhaul transport resources are notunlimited and this may result in overload of the midhaul at differentpoints (e.g., network nodes such as BBUs and/or PPUs and/or Routers) inthe transport network. In other words, there are many potentialbottlenecks where congestion may occur.

For example, the congestion may occur between BBUs and PPUs. Onepotential challenge might become the many acknowledgement (ACK) andnon-acknowledgement (NACK) messages that are communicated over themidhaul between the BBUs and PPUs. The present disclosure recognizes thefact that, in today's Long Term Evolution (LTE) evolved NodeB (eNB)deployment, the Radio Link Control (RLC) and Packet Data ConvergenceProtocol (PDCP) are co-located and any ACK and/or NACK signaling betweenthe protocol layers is typically very fast. However, the split of theRLC into the BBU and the PDCP into the PPU in the 5G RAN architecturewill most likely introduce latency. At the same time the new transportnetwork (i.e., the midhaul) between the BBU and PPU may introduceuncontrolled characteristics, like latency capacity and packet dropping.

It is in view of the above considerations and others that the variousembodiments disclosed herein have been made.

As will be appreciated, some existing solutions for congestion controlmay be inadequate, especially in the next generations (e.g., 5G orbeyond) of telecommunication networks. This disclosure recognizes thatthere is a need for a solution that allows for improved congestioncontrol.

Accordingly, it is a general object of the embodiments of the presentinvention to allow for improved congestion control. It would beadvantageous if the risk for congestion is limited, e.g. reduced orminimized. It would be particularly advantageous to provide embodimentsthat allow for a suitable congestion control in a fifth or futuregeneration telecommunications network. Furthermore, it would beadvantageous if the solution is backwards compatible with earliergeneration telecommunications networks, such as Long Term Evolution(LTE) or LTE Advanced.

In a first aspect, this disclosure concerns a method of congestioncontrol in a transport network (a.k.a. midhaul). The method is performedby a first network node. The first network node may advantageously, butnot necessarily, be a network node configured for a fifth or subsequentgeneration telecommunication network. Sometimes, the first network nodemay be referred to as a detection point throughout this disclosure.Sometimes a detection point may alternatively be referred to as anoverload point.

A buffer state of a buffer is monitored by dynamically sampling thebuffer such that the sampling rate is adjusted in dependence of thebuffer state. For example, the buffer may be a buffer which is part ofthe first network node. As will be appreciated, it is not necessary thatthe buffer is a buffer that is part of the first network node. Thebuffer may alternatively be external to the first network node.Nevertheless, in advantageous embodiments the buffer is integral withthe first network node.

Furthermore, a condition indicative of congestion is determined inresponse to a change of the buffer state exceeding a predeterminedlimit.

In response to determining the condition indicative of congestion, acongestion notification message is created, or otherwise generated. Thecongestion notification message includes a combination of: (1) a flowidentifier, and (2) back-off information.

The flow identifier may identify at least one flow that contributes tocongestion. The back-off information may indicate a suitable back-off tocompensate for the congestion caused by the at least one flow associatedwith its corresponding flow identifier.

The back-off information may include one or more of the followingparameters: back-off rate, back-off time, and ramp-up time.

Furthermore, the flow identifier may include a Packet Data ConversionProtocol (PDCP) Flow Identification (FID). Alternatively, the flowidentifier may include a PDCP Group FID. Alternatively, the flowidentifier may include a PDCP Multicast Group FID.

Additionally, the flow identifier may comprise an IP address associatedwith the first network node.

Still further, the created congestion notification message is sent, i.e.transmitted, to a second network node. Sometimes, the second networknode may be referred to as a reaction point throughout this disclosure.Sometimes a reaction point may alternatively be referred to as a balancepoint.

In some embodiments, the earlier-mentioned buffer state is the bufferfill level and the change of the buffer state is a change of the bufferfill level. The method may comprise monitoring the buffer fill level anddetermining the condition indicative of congestion in response to thebuffer fill level exceeding the predetermined limit.

In alternative embodiments, the earlier-mentioned buffer state is abuffer change rate at which the buffer changes and the change of thebuffer state is a change of the buffer change rate. The method maycomprise monitoring the rate at which the buffer state changes anddetermining the condition indicative of congestion in response to saidbuffer change rate exceeding the predetermined limit. In one embodiment,the buffer change rate is a buffer fill rate at which the buffer fillsand the buffer change rate is a buffer fill rate. The method maycomprise monitoring the rate at which the buffer state fills anddetermining the condition indicative of congestion in response to saidbuffer fill rate exceeding the predetermined limit.

In still other embodiments, it is conceivable to combine theabove-mentioned embodiments of monitoring a buffer fill level and a rateat which the buffer fills, respectively.

In a second aspect, this disclosure concerns a corresponding method ofcongestion control in a transport network (a.k.a. midhaul). The methodis performed by a second network node. The second network node mayadvantageously, but not necessarily, be a network node configured for afifth or subsequent generation telecommunication network. Sometimes, thesecond network node may be referred to as a reaction point throughoutthis disclosure. The second network node may sometimes be referred to asa reaction point throughout this disclosure. Sometimes a reaction pointmay alternatively be referred to as a balance point.

A congestion notification message is received from a first network node.

The congestion notification message includes a combination of: (1) aflow identifier, and (2) back-off information.

The flow identifier may identify at least one flow that contributes tocongestion. The back-off information may indicate a suitable back-off tocompensate for the congestion caused by the at least one flow associatedwith its corresponding flow identifier.

The back-off information may include one or more of the followingparameters: back-off rate, back-off time, and ramp-up time.

Furthermore, the flow identifier may include a Packet Data ConversionProtocol (PDCP) Flow Identification (FID). Alternatively, the flowidentifier may include a PDCP Group FID. Alternatively, the flowidentifier may include a PDCP Multicast Group FID.

Additionally, the flow identifier may comprise an IP address associatedwith the first network node.

Still further, one or more parameters are adjusted on the basis of saidback-off information.

In a third aspect, this disclosure concerns computer program, comprisinginstructions which, when executed on at least one processor, cause theat least one processor to carry out the method according to either oneor both of the above-described first and second aspects.

Furthermore, a carrier comprising said computer program may be provided.The carrier may, for example, be one of an electronic signal, an opticalsignal, a radio signal, or a computer readable storage medium.

In a fourth aspect, this disclosure concerns a first network node forcongestion control in a transport network. The first network node isconfigured to perform the method according to the earlier-describedfirst aspect.

The first network node comprises: means adapted to monitor a bufferstate of a buffer by dynamically sampling the buffer such that thesampling rate is adjusted in dependence of the buffer state of thebuffer; means adapted to determine a condition indicative of congestionin response to a change of the buffer state exceeding a predeterminedlimit; means adapted to create a congestion notification message inresponse to determining the condition indicative of congestion, thecongestion notification message including a combination of: (1) a flowidentifier; and (2) back-off information; and means adapted to transmitthe congestion notification message to a second network node.

In one example implementation, the first network node comprises atransmitter, a processor, and a memory. For example, the memory maystore computer program with instructions, which when executed on theprocessor, causes the first network node to monitor a buffer state of abuffer by dynamically sampling the buffer such that the sampling rate isadjusted in dependence of the buffer state of the buffer; determine acondition indicative of congestion in response to a change of the bufferstate exceeding a predetermined limit; in response to determining thecondition indicative of congestion, create a congestion notificationmessage including a combination of: (1) a flow identifier, and (2)back-off information; and transmit, by means of the transmitter, thecongestion notification message to a second network node.

In another example implementation, the first network node comprises afirst module configured to monitor a buffer state of a buffer bydynamically sampling the buffer such that the sampling rate is adjustedin dependence of the buffer state; a second module configured todetermine a condition indicative of congestion in response to a changeof the buffer state exceeding a predetermined limit; a third moduleconfigured to create a congestion notification message in response todetermining the condition indicative of congestion, the congestionnotification message including a combination of: (1) a flow identifier;and (2) back-off information; and means adapted to transmit thecongestion notification message to a second network node.

In a fifth aspect, this disclosure concerns a second network node forcongestion control in a transport network. The second network node isconfigured to perform the method according to the second aspect.

The second network node comprises means adapted to receive, from a firstnetwork node, a congestion notification message, wherein the congestionnotification message includes a combination of (1) a flow identifier and(2) back-off information; and means adapted to adjust one or moreparameters on the basis of said back-off information.

In one example implementation, the second network node comprises areceiver, a processor, and a memory. For example, the memory may storecomputer program with instructions, which when executed on theprocessor, causes the second network node to receive, by means of thereceiver, a congestion notification message from a first network node,wherein the congestion notification message includes a combination of(1) a flow identifier and (2) back-off information; and to adjust one ormore parameters on the basis of said back-off information.

In another example implementation, the second network node comprises areceiver configured to receive a congestion notification message from afirst network node, wherein the congestion notification message includesa combination of (1) a flow identifier and (2) back-off information, anda first module configured to adjust one or more parameters on the basisof said back-off information.

The various embodiments described herein allow for a novel mechanism forcongestion control which may be particularly suitable and/or useful fora 5G RAN architecture.

By the provision of buffer state monitoring by dynamically sampling thebuffer it is made possible to improve the congestion control. A firstnetwork node (a.k.a. detection point) creates a congestion notificationmessage in response to determining a condition indicative of congestion.This congestion notification message is transmitted to one or severalsecond network nodes (a.k.a. reaction points). Based on the receivedcongestion notification message, the one or several second network nodesmay compensate for a detected congestion by adjusting one or more of itsparameters based on received back-off information including e.g.suggested back-off time, suggested back-off rate, and/or suggestedramp-up time. Hence, a second network node may adjust i) the time duringwhich it performs back-off, ii) the rate at which back-off is performed,and/or iii) the ramp-up time for the back-off. Upon adjusting one ormore of its parameters, it is possible for the second network node toadaptively adjust its behavior in dependence of a condition indicativeof congestion detected by any first network node in the network. Thisway it is for example possible to adaptively reduce PDCPtransmissions/retransmissions in the network at appropriate times. As aresult, the transport network may operate more efficiently. As a result,also the user experience may be improved.

BRIEF DESCRIPTION OF DRAWINGS

These and other aspects, features and advantages will be apparent andelucidated from the following description of various embodiments,reference being made to the accompanying drawings, in which:

FIG. 1 illustrates an example of a midhaul architecture;

FIGS. 2A-2C are flowcharts of a method according to an embodiment;

FIGS. 3A-3D illustrate example embodiments of a congestion notificationmessage;

FIGS. 4A-4B illustrate examples in an IPv6 and a IPv4 environments,respectively,

FIG. 5 is a flowchart of a method according to an embodiment;

FIG. 6 illustrates an example embodiment of a first network node;

FIG. 7 illustrates an example implementation of the first network nodein FIG. 6;

FIG. 8 illustrates an example implementation of the first network nodein FIG. 6;

FIG. 9 illustrates an example embodiment of a second network node;

FIG. 10 illustrates an example implementation of the second network nodein FIG. 9;

FIG. 11 illustrates an example implementation of the second network nodein FIG. 9; and

FIG. 12 illustrates a carrier comprising a computer program, inaccordance with an embodiment.

DETAILED DESCRIPTION

The present invention will now be described more fully hereinafter. Thepresent invention may, however, be embodied in many different forms andshould not be construed as limited to the embodiments set forth herein;rather, these embodiments are provided by way of example so that thisdisclosure will be thorough and complete, and will fully convey thescope of the present invention to those persons who are skilled in theart. Like reference numbers refer to like elements throughout thedescription.

As described above, some existing solutions for congestion control (alsosometimes known as flow control) may be inadequate, especially in thenext generations (e.g., 5G or beyond) of telecommunication networks.This disclosure recognizes that there is a need for a solution thatallows for improved congestion control.

Accordingly, it is a general object of the embodiments of the presentinvention to allow for improved congestion control.

To address this, in accordance with an embodiment, described herein is asystem for congestion control in a transport network. The systemcomprises a first network node (a.k.a. detection point) and at least onesecond network node (a.k.a. reaction point). The first network nodemonitors a buffer state of a buffer, e.g. a buffer which is integralwith the first network node. Advantageously, the buffer is dynamicallysampled such that the sampling rate is adjusted in dependence of thebuffer state. Furthermore, the first network node determines, orotherwise detects, a condition indicative of congestion in response to achange of the buffer state exceeding a predetermined limit. In responseto determining the condition indicative of congestion, the first networknode creates a congestion notification message including a combinationof: (1) a flow identifier and (2) back-off information. Still further,the first network node transmits the congestion notification message toat least one second network node. The at least one second network nodereceives this congestion notification message. Accordingly, the at leastone second network node may, as a result, adjust one or more parameterson the basis of said back-off information.

The provision of buffer state monitoring, e.g., by dynamically samplingthe buffer state makes it possible to improve the congestion control.The first network node creates a congestion notification message inresponse to determining the condition indicative of congestion. Thiscongestion notification message is transmitted to one or several secondnetwork nodes. Based on the received congestion notification message,the one or several second network nodes may compensate for a detectedcongestion by adjusting one or more of their parameters based onreceived back-off information including e.g. suggested back-off time,back-off rate, ramp-up time. Upon adjusting one or more of theirparameters, it is possible for a second network node to adaptivelyadjust its behavior in dependence of a condition indicative ofcongestion detected by any first network node in the network. This wayit is, for example, possible to dynamically reduce PDCP transmissionsand/or retransmissions that would otherwise occur more frequentlythroughout the network. As a result, the transport network will operatemore efficiently. As a further consequence, the user experience willthus also be improved.

With reference to FIG. 2 A-C, a method according to one exampleembodiment will be described in further detail. FIG. 2A-C illustrates amethod of congestion control in a transport network. The method isperformed by a first network node. This first network node isadvantageously a network node that is configured for a fifth orsubsequent generation telecommunication network.

As can be seen in FIG. 2A, a buffer state of a buffer is monitored 210.For example, the buffer may be a buffer which is part of the firstnetwork node. In some embodiments, the buffer is thus integral with thefirst network node. As will be appreciated, it is not necessary that thebuffer is part of the first network node. In alternative embodiments,the buffer may be external to the first network node.

In advantageous embodiments, the monitoring 210 comprises dynamicallysampling the buffer such that the sampling rate is adjusted independence of the buffer state.

Furthermore, a condition indicative of congestion is determined 220 inresponse to the buffer state exceeding a predetermined limit. The exactlevel, or value, of this predetermined limit should be tested andevaluated in each specific case, e.g. in view of system requirementsand/or user demands.

In one embodiment, which is schematically illustrated in FIG. 2B, theearlier-mentioned buffer state may be a buffer fill level. Hence, thebuffer fill level may be monitored 211. Also, the condition indicativeof congestion may be determined 221 in response to the buffer fill levelexceeding the predetermined limit.

In an alternative embodiment, which is schematically illustrated in FIG.2C, the earlier-mentioned buffer state may be a buffer change rate atwhich the buffer changes. Hence, the rate at which the buffer changesmay be monitored 212. Also, the condition indicative of congestion maybe determined 222 in response to said buffer change rate exceeding thepredetermined limit. For example, the buffer change rate isadvantageously a buffer fill rate at which the buffer fills and thebuffer change rate is a buffer fill rate. Accordingly, the rate at whichthe buffer fills may be monitored 212. Also, the condition indicative ofcongestion may be determined 222 in response to said buffer fill rateexceeding the predetermined limit.

In still other embodiments, which are not illustrated in the drawings,it is conceivable to combine the above-mentioned embodiments ofmonitoring 211, 212 a buffer fill level and a rate at which the bufferchanges, respectively.

In response to determining the condition indicative of congestion (cf,YES in FIG. 2A), a congestion notification message 300 is created, orotherwise generated. As can be seen in FIG. 3A, this congestionnotification message 300 includes at least a combination of: (1) a flowidentifier 310, and (2) back-off information 320. Optionally, thecongestion notification message 300 may also include a data field 330indicating the message type, i.e. a congestion notification message.

The flow identifier 310 may identify at least one flow that contributesto congestion. The back-off information 320 may indicate a suitableback-off to compensate for the congestion caused by the at least oneflow associated with the corresponding flow identifier 310.

FIG. 3B schematically illustrates a first example implementation of thecongestion notification message 300 shown in FIG. 3A. As can be seen inFIG. 3B, the back-off information 320 may in some embodiments includeone or more of the following parameters: back-off rate 321, back-offtime 322, and ramp-up time 323. Furthermore, the flow identifier 310 mayinclude a Packet Data Conversion Protocol (PDCP) Flow Identification(FID) 311. In the example implementation shown in FIG. 3B, the Typefield defines that this is a PDCP Flow ID notification message. The PSCPFlow-ID field identifies the specific flow using the following flow IDvariant: PDCP Flow ID (PDCP-FID). The back-off rate 321 may compriseinformation about how much a second network node shall back-off. This istypically, but not necessarily, expressed in terms of rate (e.g.,bandwidth) and may e.g. be an explicit rate number or described as apercentage back-off from the instantaneously used bandwidth. Theback-off time 322 may comprise information about how long time theback-off should be performed. This is typically, but not necessarily,expressed in terms of time (e.g., seconds). The ramp-up time 323 maycomprises information about how fast the ramp-up should be, e.g., theshortest allowed time (e.g., in seconds) to get back to previous usedrate (bandwidth). The back-off rate 321, back-off time 322 and ramp-uptime 323 timer parameter values may all vary from 0 (zero), which is aspecial case, and up to an (in principle) unlimited value, which is alsoa special case.

FIG. 3C schematically illustrates a second example implementation of thecongestion notification message 300 shown in FIG. 3A. As can be seen inFIG. 3C, the flow identifier may include a PDCP Group FlowIdentification 312.

FIG. 3D schematically illustrates a third example implementation of thecongestion notification message 300 shown in FIG. 3A. As can be seen inFIG. 3D, the flow identifier may include a PDCP Multicast Group FlowIdentification 313.

With continued reference to FIG. 2, the created congestion notificationmessage 300 is also sent 240, i.e. transmitted, to a second networknode. As will be appreciated, the congestion notification message 300may be sent 240 to a single second network node, e.g. using congestionnotification message 300 as illustrated in FIG. 3B. Alternatively, thecongestion notification message 300 may be sent 240 to a group ofseveral second network nodes, e.g. using congestion notification message300 as illustrated in FIG. 3C. In still other embodiments, it ispossible to send 240 a multicast message, e.g. using congestionnotification message 300 as illustrated in FIG. 3D.

With reference to FIGS. 4A and 4B, it should be understood that the PDCPFID:s described hereinabove (e.g., PDCP-FID, PDCP-GRP-FID,PDCP-MCGRP-FID) may in some embodiments be carried by differentprotocols and in different ways. FIG. 4A shows an example in InternetProtocol version 6, IPv6. FIG. 4B shows an example in Internet Protocolversion 4, IPv4.

Reference is now made to FIG. 5, which schematically illustrates aflowchart of a corresponding method performed by a second network node.This second network node is advantageously a network node that isconfigured for a fifth or subsequent generation telecommunicationnetwork.

As can be seen in FIG. 5, a congestion notification message 300 isreceived 510 from a first network node. As can be seen in FIGS. 3A-3D,the congestion notification message 300 includes a combination of a flowidentifier 310 identifying a flow that contributes to congestion and,also, back-off information 320 indicating a suitable back-off tocompensate for the congestion caused by the flow associated with saidflow identifier. Furthermore, one or more parameters are adjusted 520,or otherwise changed, on the basis of said back-off information.

The various embodiments described herein may be applied in differentways. For example, the congestion control may be provided at IP level,managing IP flow control for PDCP over the midhaul of a 5G RAN. Thecongestion control described in this disclosure may be seen ascomprising three main parts, or functions:

1. Detection point (i.e. the first network node): the point wherecongestion is detected and congestion notification messages are sentfrom. It should be appreciated that any intermediate IP router may alsobe a detection point.2. Reaction point (i.e., the second network node(s)): the points wherethe action is taken on congestion based on received congestionnotification message. It should be appreciated that any intermediate IProuter may also be a reaction point.3. Congestion Notification Messages: The messages sent between detectionpoints and the reaction points, informing the reaction points ofcongestion and including back-off information to assist reaction pointsin compensating for a detected congestion.

In some embodiments and for traffic in the PDCP domain, the PDCP flow(s)may be marked with PDCP Flow ID (PDCP-FID, single PDCP flow) and/or(PDCP-GRP-FID, for PDCP group flows), which may for instance be encodedinto the IP flow ID header (IPv6), or in a separate IP option, or anykind of protocol header.

When the detection point identifies congestion it may also detect theflow(s) that consume most of the bandwidth. This may, e.g., be performedby identifying the packets that are consuming most of the buffer or,alternatively, by flow sampling statistics. The detection point willthen send a notification message to the reaction point, e.g. using thesource IP-address and PDCP-FID/PDCP-GRP-FID of the identified flow(s).In case of sending the message to multiple reaction points at the sametime, multicast may be used as an alternative. In the latter case, aMulticast PDCP group notification FID (PDCP-MCGRP-FID) may be used. Thismay be utilized in both downlink and uplink direction. As describedearlier, the congestion notification message 300 may include back-offinformation 320 such as information of time to pause sending and/orlevel of back off.

In some embodiments, it is possible to use or otherwise utilize“watermarks”. The working principle of a detection point may then be asfollows. The water marks in each Quality-of-Service (QoS) queue ischecked together with the related Source IP-address including PDCP-FIDand/or PDCP-GRP-FID. The sampling of the buffer is dynamic, meaning thatwhen there is high buffer occupation the sampling rate is increased andwhen the buffer occupation is low the sampling rate is lower. When thewatermark is passed, the detection point may send a congestionnotification message to the reaction point identified by IP-address andrelated PDCP-FID and/or PDCP-GRP-FID. When multicast is used thedetection point may send to the multicast source specific IP group andmay use the related PDCP-MCGRP-FID. As described earlier, the congestionnotification message may for example comprise information on i) how much(expressed as rate) the reaction point(s) should back off, ii) for howlong time (expressed in time) the reaction point(s) should back off andiii) the ramp-up time after a back-off. For further details with respectto the congestion notification messages, see FIGS. 3A-3D.

A dynamical sampling makes it possible to adaptively adjust, orotherwise change, the sampling rate. For example, when the trafficintensity is low and thus a buffer fill level is low, the sampling ratemay also be adjusted to be low as there is typically no (or, little)need for detailed flow information. Furthermore, when the trafficintensity is low it may be advantageous to reduce the sampling rate asthis will also limit the usage of processing resources and power.However, when the traffic intensity increases the sampling rate may alsobe adjusted to increase, e.g., to make it easier to identify the flow(s)that is/are consuming most bandwidth.

In the reaction point(s), the flow(s) may be identified by the PDCP-FIDand/or PDCP-GRP-FID and/or PDCP-MCGRP-FID. For example, the reactionpoint(s), the information received in the notification message may beused to adapt the PDCP scheduler and/or buffer allocation. This mayreduce the total bandwidth that is consumed from the reaction point(s)towards the detection point node.

Reference is now made to FIG. 6, which illustrates an example embodimentof a first network node 10. The first network node is configured toperform, or otherwise carry out, any of the methods described withreference to FIGS. 2A-2C. The first network node 10 is advantageously anetwork node configured for a 5G or subsequent generationtelecommunications network.

The first network node 10 is suitable for congestion control, a.k.a.flow control, in a transport network. As can be seen in FIG. 6, thefirst network node 10 comprises means 11 adapted to monitor a bufferstate of a buffer by dynamically sampling the buffer such that thesampling rate is adjusted in dependence of the buffer state.Furthermore, means 12 are provided to determine a condition indicativeof congestion in response to a change of the buffer state exceeding apredetermined limit. Also, means 13 are provided to create a congestionnotification message 300 (see FIGS. 3A-3D) in response to determiningthe condition indicative of congestion. As described earlier, thecongestion notification message includes a combination of a flowidentifier identifying a flow that contributes to congestion andback-off information indicating a suitable back-off to compensate forthe congestion caused by the flow associated with said flow identifier.As also described earlier, the back-off information includes one or moreof the following parameters: back-off rate, back-off time, ramp-up time.The flow identifier may e.g. include a PDCP FID, a PDCP Group FID or aPDCP Multicast Group FID. Optionally, the flow identifier mayadditionally comprise an IP address associated with the first networknode. With continued reference to FIG. 6, the first network node 10additionally comprises means 14 adapted to transmit the congestionnotification message to a second network node.

In some embodiments, the buffer state is a buffer fill level and thechange of the buffer state is a change of the buffer fill level. Hence,the first network node 10 may comprise means 11 adapted to monitor thebuffer fill level as well as means 12 adapted to determine the conditionindicative of congestion in response to the buffer fill level exceedingthe predetermined limit.

In some embodiments, the buffer state is a buffer change rate at whichthe buffer changes and the change of the buffer state is a change of thebuffer change rate. Hence, the first network node 10 may comprise means11 adapted to monitor the rate at which the buffer state changes andmeans 12 adapted to determine the condition indicative of congestion inresponse to said buffer change rate exceeding the predetermined limit.In one embodiment, the buffer change rate is a buffer fill rate at whichthe buffer fills and the buffer change rate is a buffer fill rate.Accordingly, the first network node 10 may be provided with means 11adapted to monitor the rate at which the buffer state fills; and means12 adapted to determine the condition indicative of congestion inresponse to said buffer fill rate exceeding the predetermined limit.

FIG. 7 illustrates an example implementation of the first network node10 illustrated in FIG. 6. In this example implementation, the firstnetwork node 10 comprises a processor 15 and a memory 16. Also, acommunications interface 17 may be provided in order to allow the firstnetwork node to communicate with other apparatuses (e.g., one or severalsecond network nodes), etc. To this end, the communications interface 17may comprise a transmitter (Tx) and a receiver (Rx). Alternatively, thecommunications interface 17 may comprise a transceiver (Tx/Rx) combiningboth transmission and reception capabilities. The communicationsinterface 17 may include a RF interface allowing the first network nodeto communicate with apparatuses etc through a radio frequency bandthrough the use of different radio frequency technologies e.g.standardized by the 3rd Generation Partnership Project (3GPP), or anyother wireless technology such as Wi-Fi, Bluetooth®, etcetera.

The memory 16 comprises instructions executable by the processor 15whereby the first network node 10 is operative to:

monitor the buffer state of the buffer by dynamically sampling thebuffer such that the sampling rate is adjusted in dependence of thebuffer state,

determine a condition indicative of congestion in response to a changeof the buffer state exceeding a predetermined limit, and

create a congestion notification message in response to determining thecondition indicative of congestion, wherein the congestion notificationmessage includes the earlier-described combination of: (1) a flowidentifier identifying a flow that contributes to congestion; and (2)back-off information indicating a suitable back-off to compensate forthe congestion caused by the flow associated with said flow identifier;and

transmit, by means of the transmitter, the congestion notificationmessage to a second network node.

In some embodiments, the memory 16 further comprises instructionsexecutable by the processor 15 whereby the first network node 10 isoperative to:

monitor the buffer fill level; and

determine the condition indicative of congestion in response to thebuffer fill level exceeding the predetermined limit.

In some embodiments, the memory 16 further comprises instructionsexecutable by the processor 15 whereby the first network node 10 isoperative to:

monitor the rate at which the buffer state changes; and

determine the condition indicative of congestion in response to saidbuffer change rate exceeding the predetermined limit.

In some embodiments, the memory 16 further comprises instructionsexecutable by the processor 15 whereby the first network node 10 isoperative to:

monitor the rate at which the buffer state fills; and

determine the condition indicative of congestion in response to saidbuffer fill rate exceeding the predetermined limit.

Reference is now made to FIG. 8, which illustrates another exampleimplementation of the first network node 10. In this exampleimplementation, the first network node 10 comprises a processor 18, andone or several modules 19 a-c. Also, a communications interface may beprovided in order to allow the first network node 10 to communicate withother apparatuses (e.g., one or several second network nodes), etc. Tothis end, the communications interface may comprise a transmitter (Tx)and/or a receiver (Rx). Alternatively, the communications interface maycomprise a transceiver (Tx/Rx) combining both transmission and receptioncapabilities. The communications interface may include a RF interfaceallowing the first network node 10 to communicate with apparatuses etcthrough a radio frequency band through the use of different radiofrequency technologies e.g. standardized by the 3rd GenerationPartnership Project (3GPP), or any other wireless technology such asWi-Fi, Bluetooth®, etcetera.

A buffer state monitoring module 19 a is configured to monitor thebuffer by dynamically sampling the buffer such that the sampling rate isadjusted in dependence of the buffer state. Furthermore, a congestiondetection module 19 b is configured to determine a condition indicativeof congestion in response to a change of the buffer state exceeding apredetermined limit. Still further, a congestion notification messagegeneration module 19 c is configured to create or otherwise generate acongestion notification message in response to determining the conditionindicative of congestion. As described earlier, the created congestionnotification message includes a combination of: (1) a flow identifieridentifying a flow that contributes to congestion; and (2) back-offinformation indicating a suitable back-off to compensate for thecongestion caused by the flow associated with said flow identifier.Moreover, a transmitter (Tx) may be configured to transmit the createdcongestion notification message to one or more second network nodes.

In some embodiments, the buffer state monitoring module 19 a isconfigured to monitor the buffer fill level and the congestion detectionmodule 19 b is configured to determine the condition indicative ofcongestion in response to the buffer fill level exceeding thepredetermined limit.

In some embodiments, the buffer state monitoring module 19 a isconfigured to monitor the rate at which the buffer state changes and thecongestion detection module 19 b is configured to determine thecondition indicative of congestion in response to said buffer changerate exceeding the predetermined limit. For example, in one embodiment,the buffer state monitoring module 19 a is configured to monitor therate at which the buffer state fills and the congestion detection module19 b is configured to determine the condition indicative of congestionin response to said buffer fill rate exceeding the predetermined limit.

Reference is now made to FIG. 9, which illustrates an example embodimentof a second network node 30. The second network node 30 is configured toperform, or otherwise carry out, any of the method described withreference to FIG. 5. The second network node 30 is advantageously anetwork node configured for a 5G or a subsequent generationtelecommunications network.

The second network node 30 is suitable for congestion control, a.k.a.flow control, in a transport network. As can be seen in FIG. 9, thesecond network node 30 comprises means 31 adapted to receive, from afirst network node, a congestion notification message 300. As describedearlier, the congestion notification message 300 includes a combinationof: (1) a flow identifier 310 identifying a flow that contributes tocongestion and (2) back-off information 320 indicating a suitableback-off to compensate for the congestion caused by the flow associatedwith said flow identifier. Furthermore, the second network node 30comprises means 32 adapted to adjust one or more parameters on the basisof said back-off information.

FIG. 10 illustrates an example implementation of the second network node30 illustrated in FIG. 9. In this example implementation, the secondnetwork node 30 comprises a processor 33 and a memory 34. Also, acommunications interface 35 may be provided in order to allow the firstnetwork node to communicate with other apparatuses (e.g., a firstnetwork node), etc. To this end, the communications interface 35 maycomprise a transmitter (Tx) and a receiver (Rx). Alternatively, thecommunications interface 35 may comprise a transceiver (Tx/Rx) combiningboth transmission and reception capabilities. The communicationsinterface 35 may include a RF interface allowing the first network nodeto communicate with apparatuses etc through a radio frequency bandthrough the use of different radio frequency technologies e.g.standardized by the 3rd Generation Partnership Project (3GPP), or anyother wireless technology such as Wi-Fi, Bluetooth®, etcetera.

The memory 34 comprises instructions executable by the processor 33whereby the second network node 30 is operative to:

receive (from a first network node) a congestion notification message bymeans of the receiver 35, wherein the congestion notification messageincludes said combination of a flow identifier identifying a flow thatcontributes to congestion and back-off information indicating a suitableback-off to compensate for the congestion caused by the flow associatedwith said flow identifier; and

adjust one or more parameters on the basis of said back-off information.

Reference is now made to FIG. 11, which illustrates another exampleimplementation of the second network node 30. In this exampleimplementation, the second network node 30 comprises a processor 36, andone or several modules 37 a. Also, a communications interface may beprovided in order to allow the second network node 30 to communicatewith other apparatuses (e.g., a first network node), etc. To this end,the communications interface may comprise a transmitter (Tx) and/or areceiver (Rx). Alternatively, the communications interface may comprisea transceiver (Tx/Rx) combining both transmission and receptioncapabilities. The communications interface may include a RF interfaceallowing the second network node 30 to communicate with apparatuses etcthrough a radio frequency band through the use of different radiofrequency technologies e.g. standardized by the 3rd GenerationPartnership Project (3GPP), or any other wireless technology such asWi-Fi, Bluetooth®, etcetera.

The receiver (Rx) is configured to receive the congestion notificationmessage, wherein the congestion notification message includes saidcombination of a flow identifier identifying a flow that contributes tocongestion and back-off information indicating a suitable back-off tocompensate for the congestion caused by the flow associated with saidflow identifier. Also, a parameter adjustment module 37 a is configuredto adjust or otherwise change one or more parameters on the basis ofsaid back-off information.

FIG. 12 shows an example of a computer-readable medium, in this examplein the form of a data disc 1200. In one embodiment the data disc 1200 isa magnetic data storage disc. The data disc 1200 is configured to carryinstructions 1210 that can be loaded into a memory of an apparatus. Uponexecution of said instructions by a processor of the apparatus, theapparatus is caused to execute a method or procedure according to anyone of the methods described in this disclosure. The data disc 1200 isarranged to be connected to or within and read by a reading device (notshown), for loading the instructions into the processor. One suchexample of a reading device in combination with one (or several) datadisc(s) 1200 is a hard drive. It should be noted that thecomputer-readable medium can also be other mediums such as compactdiscs, digital video discs, flash memories or other memory technologiescommonly used. In such an embodiment the data disc 1200 is one type of atangible computer-readable medium. The instructions may alternatively bedownloaded to a computer data reading device, such as a computer orother apparatus capable of reading computer coded data on acomputer-readable medium, by comprising the instructions in acomputer-readable signal (not shown) which is transmitted via a wireless(or wired) interface (for example via the Internet) to the computer datareading device for loading the instructions into a processor of theapparatus. In such an embodiment, the computer-readable signal is onetype of a non-tangible computer-readable medium.

The various embodiments described throughout this disclosure areadvantageous in that a buffer state may be monitored by dynamicallysampling the buffer. Hereby, it is made possible to improve thecongestion control. A first network node (a.k.a. detection point)creates a congestion notification message in response to determining acondition indicative of congestion. This congestion notification messageis transmitted to one or several second network nodes (a.k.a. reactionpoints). Based on the received congestion notification message, the oneor several second network nodes may compensate for a detected congestionby adjusting one or more of its parameters based on received back-offinformation including e.g. suggested back-off time, suggested back-offrate, and/or suggested ramp-up time. Hence, a second network node mayadjust i) the time during which it performs back-off, ii) the rate atwhich back-off is performed, and/or iii) the ramp-up time for theback-off. Upon adjusting one or more of its parameters, it is possiblefor the second network node to adaptively adjust its behavior independence of a condition indicative of congestion detected by any firstnetwork node in the network. This way it is for example possible toadaptively reduce PDCP transmissions/retransmissions in the network atappropriate times. As a result, the transport network may operate moreefficiently. As a result, also the user experience may be improved.

In the detailed description hereinabove, for purposes of explanation andnot limitation, specific details are set forth in order to provide athorough understanding of various embodiments described in thisdisclosure. In some instances, detailed descriptions of well-knowndevices, components, circuits, and methods have been omitted so as notto obscure the description of the embodiments disclosed herein withunnecessary detail. All statements herein reciting principles, aspects,and embodiments disclosed herein, as well as specific examples thereof,are intended to encompass both structural and functional equivalentsthereof. Additionally, it is intended that such equivalents include bothcurrently known equivalents as well as equivalents developed in thefuture, i.e., any elements developed that perform the same function,regardless of structure. Thus, for example, it will be appreciated thatblock diagrams herein can represent conceptual views of illustrativecircuitry or other functional units embodying the principles of thedescribed embodiments. Similarly, it will be appreciated that any flowcharts and the like represent various processes which may besubstantially represented in computer readable medium and so executed bya computer or processor, whether or not such computer or processor isexplicitly shown. The functions of the various elements includingfunctional blocks, may be provided through the use of hardware such ascircuit hardware and/or hardware capable of executing software in theform of coded instructions stored on the above-mentioned computerreadable medium. Thus, such functions and illustrated functional blocksare to be understood as being either hardware-implemented and/orcomputer-implemented, and thus machine-implemented. In terms of hardwareimplementation, the functional blocks may include or encompass, withoutlimitation, digital signal processor (DSP) hardware, reduced instructionset processor, hardware (e.g., digital or analog) circuitry includingbut not limited to application specific integrated circuit(s) (ASIC(s)),and/or field programmable gate array(s) (FPGA(s)), and (whereappropriate) state machines capable of performing such functions. Interms of computer implementation, a computer is generally understood tocomprise one or more processors or one or more controllers. Whenprovided by a computer or processor or controller, the functions may beprovided by a single dedicated computer or processor or controller, by asingle shared computer or processor or controller, or by a plurality ofindividual computers or processors or controllers, some of which may beshared or distributed. Moreover, use of the term “processor” or“controller” may also be construed to refer to other hardware capable ofperforming such functions and/or executing software, such as the examplehardware recited above.

Modifications and other variants of the described embodiments will cometo mind to one skilled in the art having benefit of the teachingspresented in the foregoing description and associated drawings.Therefore, it is to be understood that the embodiments are not limitedto the specific example embodiments described in this disclosure andthat modifications and other variants are intended to be included withinthe scope of this disclosure. As a mere example, it should beappreciated that it is conceivable to use or otherwise utilize several(i.e., two or more) predetermined limits. This way it may for instancebe possible to determine different levels of congestion, e.g. from lowcongestion to high congestion. Also, the back-off information indicatingthe suitable back-off to compensate for the congestion may be tailoredto compensate for said different levels of congestion.

Furthermore, although specific terms may be employed herein, they areused in a generic and descriptive sense only and not for purposes oflimitation. Therefore, a person skilled in the art would recognizenumerous variations to the described embodiments that would still fallwithin the scope of the appended claims. As used herein, the terms“comprise/comprises” or “include/includes” do not exclude the presenceof other elements or steps. Furthermore, although individual featuresmay be included in different embodiments, these may possiblyadvantageously be combined, and the inclusion of different numberedembodiments does not imply that a combination of features is notfeasible and/or advantageous. In addition, singular references do notexclude a plurality.

1. A method of congestion control in a transport network, the methodbeing performed by a first network node and comprising: monitoring (210)a buffer state of a buffer by dynamically sampling the buffer such thatthe sampling rate is adjusted in dependence of the buffer state;determining (220) a condition indicative of congestion in response to achange of the buffer state exceeding a predetermined limit; in responseto determining (220) the condition indicative of congestion, creating(230) a congestion notification message (300) including a combinationof: i) a flow identifier (310) identifying a flow that contributes tocongestion; and ii) back-off information (320) indicating a suitableback-off to compensate for the congestion caused by the flow associatedwith said flow identifier (310); and transmitting (240) the congestionnotification message (300) to a second network node.
 2. The method ofclaim 1, wherein the buffer state is the buffer fill level and thechange of the buffer state is a change of the buffer fill level, themethod comprising: monitoring (211) the buffer fill level; anddetermining (221) the condition indicative of congestion in response tothe buffer fill level exceeding the predetermined limit.
 3. The methodof claim 1, wherein the buffer state is a buffer change rate at whichthe buffer changes and the change of the buffer state is a change of thebuffer change rate, the method comprising: monitoring (212) the rate atwhich the buffer state changes; and determining (222) the conditionindicative of congestion in response to said buffer change rateexceeding the predetermined limit.
 4. The method of claim 3, wherein thebuffer change rate is a buffer fill rate at which the buffer fills andthe buffer change rate is a buffer fill rate, the method comprising:monitoring (212) the rate at which the buffer state fills; anddetermining (222) the condition indicative of congestion in response tosaid buffer fill rate exceeding the predetermined limit.
 5. The methodof any one of the claims 1-4, wherein the back-off information (320)includes one or more of the following parameters: back-off rate (321),back-off time (322), ramp-up time (323).
 6. The method of any one of theclaims 1-5, wherein the flow identifier (310) includes a Packet DataConversion Protocol, PDCP, Flow Identification, FID.
 7. The method ofany one of the claims 1-5, wherein the flow identifier (310) includes aPDCP Group FID.
 8. The method of any one of the claims 1-5, wherein theflow identifier (310) includes a PDCP Multicast Group FID.
 9. The methodof any one of the claims 5-8, wherein the flow identifier (310)additionally comprises an Internet Protocol, IP, address associated withthe first network node.
 10. A method of congestion control in atransport network, the method being performed by a second network nodeand comprising: receiving (510), from a first network node, a congestionnotification message (300), wherein the congestion notification message(300) includes a combination of: i) a flow identifier (310) identifyinga flow that contributes to congestion; and ii) back-off information(320) indicating a suitable back-off to compensate for the congestioncaused by the flow associated with said flow identifier; and adjusting(520) one or more parameters on the basis of said back-off information.11. The method of claim 10, wherein the back-off information (320)includes one or more of the following parameters: back-off rate (321),back-off time (322), ramp-up time (323).
 12. The method of claim 10 or11, wherein the flow identifier (310) includes a Packet Data ConversionProtocol, PDCP, Flow Identification, FID.
 13. The method of claim 10 or11, wherein the flow identifier (310) includes a PDCP Group FID.
 14. Themethod of claim 10 or 11, wherein the flow identifier (310) includes aPDCP Multicast Group FID.
 15. The method of any one of the claims 10-14,wherein the flow identifier (310) additionally comprises an InternetProtocol, IP, address associated with the first network node. 16.Computer program, comprising instructions which, when executed on atleast one processor, cause the at least one processor to carry out themethod according to any one of claims 1-15.
 17. A carrier comprising thecomputer program of the claim 16, wherein the carrier is one of anelectronic signal, an optical signal, a radio signal, or a computerreadable storage medium.
 18. A first network node (10) for congestioncontrol in a transport network, the first network node (10) comprising:means (11) adapted to monitor a buffer state of a buffer by dynamicallysampling the buffer such that the sampling rate is adjusted independence of the buffer state; means (12) adapted to determine acondition indicative of congestion in response to a change of the bufferstate exceeding a predetermined limit; means (13) adapted to create acongestion notification message (300) in response to determining thecondition indicative of congestion, the congestion notification message(300) including a combination of: i) a flow identifier (310) identifyinga flow that contributes to congestion; and ii) back-off information(320) indicating a suitable back-off to compensate for the congestioncaused by the flow associated with said flow identifier; and means (14)adapted to transmit the congestion notification message to a secondnetwork node.
 19. The first network node (10) of claim 18, wherein thebuffer state is the buffer fill level and the change of the buffer stateis a change of the buffer fill level, the first network node comprising:means (11) adapted to monitor the buffer fill level; and means (12)adapted to determine the condition indicative of congestion in responseto the buffer fill level exceeding the predetermined limit.
 20. Thefirst network node (10) of claim 18, wherein the buffer state is abuffer change rate at which the buffer changes and the change of thebuffer state is a change of the buffer change rate, the first networknode comprising: means (11) adapted to monitor the rate at which thebuffer state changes; and means (12) adapted to determine the conditionindicative of congestion in response to said buffer change rateexceeding the predetermined limit.
 21. The first network node (10) ofclaim 20, wherein the buffer change rate is a buffer fill rate at whichthe buffer fills and the buffer change rate is a buffer fill rate, themethod comprising: means (11) adapted to monitor the rate at which thebuffer state fills; and means (12) adapted to determine the conditionindicative of congestion in response to said buffer fill rate exceedingthe predetermined limit.
 22. The first network node (10) of any one ofthe claims 18-21, wherein the back-off information (320) includes one ormore of the following parameters: back-off rate (321), back-off time(322), ramp-up time (323).
 23. The first network node (10) of any one ofthe claims 18-22, wherein the flow identifier (310) includes a PacketData Conversion Protocol, PDCP, Flow Identification, FID.
 24. The firstnetwork node (10) of any one of the claims 18-22, wherein the flowidentifier (310) includes a PDCP Group FID.
 25. The first network node(10) of any one of the claims 18-22, wherein the flow identifier (310)includes a PDCP Multicast Group FID.
 26. The first network node (10) ofany one of the claims 18-22, wherein the flow identifier (310)additionally comprises an Internet Protocol, IP, address associated withthe first network node.
 27. A second network node (30) for congestioncontrol in a transport network, the second network node comprising:means (31) adapted to receive, from a first network node, a congestionnotification message (300), wherein the congestion notification message(300) includes a combination of: i) a flow identifier (310) identifyinga flow that contributes to congestion; and ii) back-off information(320) indicating a suitable back-off to compensate for the congestioncaused by the flow associated with said flow identifier; and means (32)adapted to adjust one or more parameters on the basis of said back-offinformation (320).
 28. The second network node (30) of claim 27, whereinthe back-off information (320) includes one or more of the followingparameters: back-off rate (321), back-off time (322), ramp-up time(323).
 29. The second network node (30) of claim 27 or 28, wherein theflow identifier (310) includes a Packet Data Conversion Protocol, PDCP,Flow Identification, FID.
 30. The second network node (30) of claim 27or 28, wherein the flow identifier (310) includes a PDCP Group FID. 31.The second network node (30) of claim 27 or 28, wherein the flowidentifier (310) includes a PDCP Multicast Group FID.
 32. The secondnetwork node (30) of any one of the claims 27-31, wherein the flowidentifier (310) additionally comprises an Internet Protocol, IP,address associated with the first network node.